U.S. patent number 4,705,839 [Application Number 07/032,892] was granted by the patent office on 1987-11-10 for urethane nonaqueous dispersion for automotive base coat/clear coat applications.
This patent grant is currently assigned to BASF Corporation, Inmont Division. Invention is credited to Glenn E. Martin.
United States Patent |
4,705,839 |
Martin |
November 10, 1987 |
Urethane nonaqueous dispersion for automotive base coat/clear coat
applications
Abstract
The present invention discloses a nonaqueous dispersion of
urethane copolymers dispersed in a solvent which is less polar than
the urethane copolymer segment wherein the urethane copolymers are
the reaction products of a stabilizer, an aliphatic polyol and
diisocyanates. Also disclosed is a method for making the nonaqueous
polyurethane dispersions.
Inventors: |
Martin; Glenn E. (Farmington
Hills, MI) |
Assignee: |
BASF Corporation, Inmont
Division (Clifton, NJ)
|
Family
ID: |
21867416 |
Appl.
No.: |
07/032,892 |
Filed: |
March 31, 1987 |
Current U.S.
Class: |
528/49 |
Current CPC
Class: |
C08G
18/284 (20130101); C08J 3/09 (20130101); C08J
2375/04 (20130101) |
Current International
Class: |
C08G
18/00 (20060101); C08G 18/28 (20060101); C08J
3/09 (20060101); C08J 3/02 (20060101); C08G
018/32 () |
Field of
Search: |
;528/49 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Welsh; Maurice J.
Attorney, Agent or Firm: Chipaloski; M. R.
Claims
I claim:
1. A nonaqueous dispersion particularly adapted for use in
automotive base coat/clear coat applications comprising:
a urethane copolymer dispersed throughout a solvent, said solvent
being less polar than the urethane copolymer, wherein said urethane
copolymer is the reaction product of a stabilizer, polyols, and
diisocyanate, and said stabilizer is the reaction product of a
carboxylic acid and a monoepoxide, said nonaqueous dispersion when
used to produce automotive base coats results in a high solids, low
viscosity base coat with good rheology control.
2. A method of making a nonaqueous dispersion for use in automotive
base coat/clear coat applications comprising:
preparing a stabilizer by reacting a carboxylic acid with a
monoepoxide;
reacting the stabilizer with polyols and diisocyanate to produce a
urethane copolymer, dispersing the copolymer in a solvent having a
polarity less than that of the copolymer to form a nonaqueous
dispersion.
3. The dispersion of claim 1 wherein the urethane copolymer is a
polyester polyurethane.
4. The method of claim 2 wherein the urethane copolymer is a
polyester polyurethane.
Description
DESCRIPTION
1. Technical Field
The present invention pertains to nonaqueous dispersions
particularly those nonaqueous dispersions useful in automotive
finishing procsesses.
2. Background Art
Due to the increase in costs and regulatory controls which have
been placed on organic solvents, the paint industry has been trying
to reduce the use of these materials in their products. One method
has been to increase the solids content of the coating solution,
but unfortunately, the resulting coatings fall short of industry
standards. One particular problem has been the inability to develop
a high solids coating which will result in the proper metal
orientation of the metal flakes dispersed throughout the coating,
without the use of expensive rheology control agents. These metal
flakes are added to the base coat to enhance the mirrored finish
and depth of the color. In addition, when the metal flakes are
oriented in the proper direction, the brightness varies vis-a-vis
the direction in which the light strikes it. These are highly
desirable qualities in paint functions for the automobile industry.
It has been found that through the addition of rheology control
agents the metal orientation can be achieved in the higher solids
base coats. However, this material added to the coat results in a
loss in quality of the final base coat. These rheology control
agents aid in orienting the metal particles such that the resulting
coating has good aluminum control.
Therefore, what is needed in this art area is high solids (above
40% by weight) base coat polymer which will result in proper metal
orientation to produce the desired finish, without the use of
rheology control agents.
DISCLOSURE OF INVENTION
The present invention discloses a nonaqueous dispersion of urethane
copolymers dispersed in a solvent which is less polar than the
urethane copolymer segment, the urethane copolymers being the
reaction product of a stabilizer, aliphatic polyols and
diisocyanates. The particular stabilizers which are used to make
these dispersions are the reaction products of a carboxylic acid
and a monoepoxide.
Also disclosed is a method for making the nonaqueous dispersion
wherein a stabilizer is prepared by reacting a carboxylic acid with
a monoepoxide, then reacting this stabilizer with polyols and
diisocyanates to form the nonaqueous dispersion urethane polymer
which when dispersed in a solvent which is less polar than the
urethane polymer segment to form the nonaqueous dispersion.
These base coats will allow for the production of base coat
solutions which have higher solids content yet do not have the
higher viscosity so often associated with the increase in polymeric
content. This means that less organic solvents need to be used when
preparing the base coat for application to the substrates and also
that the proper metal orientation will be maintained without the
use of the rheology reagents which are so often required when
higher solids products are used, resulting in a superior finish
which is less harmful to the environment and less costly to
apply.
Other features and advantages of the present invention will become
more apparent from the following detailed description of the
preferred embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
The stabilizers which are useful in this invention are hydroxy
functional reaction products of a carboxylic acid and a
monoepoxide. ##STR1## where R may be any alihatic, branched or
straight chain constituent and R' may be any aliphatic
constituent.
The carboxylic acid may be any aliphatic carboxylic acid
commercially available or may be the result of the reaction between
monofunctional alcohols and a cyclic anhydride. ##STR2##
The monofunctional alcohol may be aromatic or aliphatic, straight
chain or branched and may contain other functional groups which do
not interfere with the formation of the carboxylic intermediate or
its subsequent reaction with the monoepoxide. Examples of alcohols
which may be used are methanol, ethanol, butanol, iso-butanol,
benzyl alcohol, 2-ethylhexanol, propanol, iso-propanol and
cyclohexanol.
The cyclic anhydrides used may be any anhydrides which will form a
carboxylic acid when reacted with monofunctional alcohols, and may
be aromatic, aliphatic, straight chain or branched. Typical
anhydrides are maleic anhydride, phthalic anhydride, succinic
anhydride, and glutaric anhydride.
The resulting carboxylic acid is then reacted with an aliphatic
monoepoxide which may be straight chain or branched. Some
commercially available epoxides which may be used are Cardura
E.RTM. epoxide which is a glycidyl ester of versatic acid and is
available from the Shell Oil Company, and AZ Epoxy No. 8.RTM.
epoxide which is a mixture of C.sub.12 -C.sub.14 monoglycidyl ether
from AZS Corporation in Atlanta, GA.
The reaction to form the hydroxyl functional stabilizer from these
reactants is conventional and comprises a conventional stepwise
addition reaction. In the case where the carboxylic acid is formed
initially from the alcohol and the anhydride, the reactants are
present in a molar relation of about 1:1, this is also the molar
relationship of the reactants when the monoepoxide is reacted with
the carboxylic acid.
Two examples of stabilizers which were prepared and were used in
preparation of nonaqueous dispersions follow.
EXAMPLE I
To a reaction flask equipped with an agitator, thermometer,
condenser and a nitrogen inlet tube, 114 grams of ethylene glycol
monoethyl etheracetate, 65 gm of 2-ethylhexanol and 50 grams of
succinic anhydride were added. The reaction mixture was heated to
145.degree. C. and held until an acid number of about 122 is
reached. At this time, 143 gm of AZ Epoxy No. 8.RTM. (C.sub.12
-C.sub.14 monoglycidyl ether) was added along with 1.3 gm of benzyl
dimethylamine. The batch was held again at a temperature of
145.degree. C., until an acid number of ten or less was reached. At
this time 50 gm of succinic anhydride was added and the batch was
held at 145.degree. C. until an acid number of 81 was reached. A
final addition of 200.2 gm of the AZ Epoxy No. 8.RTM. was added and
the batch held until an acid number of 1.8 was reached. The batch
was then cooled to below about 100.degree. C. and stored for later
use. The resulting stabilizer solution had a solids content of 82%
by weight.
EXAMPLE II
To a reaction flask equipped with an agitator, thermometer,
condenser and a nitrogen inlet tube, 120 gm of ethylene glycol
monoethyl ether acetate, 75.4 gm of 2-ethyl hexanol and 58 gm of
succinic anhydride were added and the reaction mixture was heated
to 130.degree. C. and held until an acid number of about 133.6 is
reached. At this time 145 gm of Cardura E (glycidyl ester of
versatic acid) was added. The batch was held until an acid number
of 13 or less was reched. At this time 58 gm of succinic anhydride
was added and the batch was held at 145.degree. C. until an acid
number of 84 was reached. A final addition of 145 gm of the Cardura
E was added and the batch held at temperature until an acid number
of 8.3 was reached. The batch was then cooled to below 100.degree.
C. and stored for later use. The resulting stabilizer solution had
a solids content of 79.5% by weight.
It has been determined that to optimize certain characteristics of
the nonaqueous dispersion, that the stabilizers have a higher
molecular weight than those which result from a single addition
reaction of the commercially available acids and epoxides.
Typically, stabilizers should have molecular weights (weight
average) from about 500 to about 1300 while the preferred are about
800 to about 1100. This may be achieved by reacting the hydroxyl
functional stabilizer resulting from the monoepoxide and carboxylic
acid reaction with more cyclic anhydride to again produce a
carboxylic acid which when reacted with more monoepoxide results in
a larger molecular weight hydroxyl functional stabilizer. The cycle
may be repeated any number of times until the desired molecular
weight stabilizer is attained, such stabilizers will also have
increased aliphatic properties which are desirable as it they
increase the stability in nonpolar solvents.
The resulting stabilizer described above may then be reacted with
polyols and diisocyanates to produce a urethane polymer which when
dispersed in a solvent having a lower polarity than the urethane
will result in the stable nonaqueous dispersion.
This reaction is a conventional urethane condensation reaction
between the stabilizer, aliphatic polyols and diisocyanate.
Both the polyols and the diisocyanates which may be used are those
typically used for making urethane resins.
The polyols may be aliphatic, cycloaliphatic, or branched
aliphatic. Some typical ones which may be used are ethylene glycol,
neo-pentyl glycol 1,4-butane diol, 1,6-hexane diol, cyclohexane
dimethylol, trimethylol propane, trimethylol ethane, etc. Although
a certain amount of aromaticity may be tolerated in the polyols it
is not desirable as they are not ultraviolet durable and they would
be less desirable where the finish is to be used in automobile
coatings.
The diisocyanates may also be any of those commonly used in the
manufacture of urethane resins. These are, again, aliphatic, cyclic
aliphatic branched or straight chained, two examples of which are
isophorone diisocyanate and dicylohexyl
methane-4,4'-diisocyanate.
Typically, the reactants, the stabilizer, the diisocyanate and the
polyols are placed in a reaction flask and are reacted under
conventional polyurethane forming conditions. This means heating
the reactors to about 75.degree. C. to about 150.degree. C. until
about 98% or higher of diisocyanate has been reacted.
The reactants should be present in such a relationship that the
stabilizer comprises about 8% to about 35% by weight where about
11% to about 13% by weight is preferred, the diisocyanate is
present at about 15% to about 55% by weight with about 30% to about
45% by weight is preferred, and the balance is the polyols. It is
important to the success of this reaction to maintain a ratio of
OH/.sub.NCO (between the polyols and diisocyanate) of about 1.02 to
about 1.5 and preferably about 1.4.
Although the nonaqueous dispersions of polyurethane copolymers may
be used to prepare useful dispersions, it is preferred that the
urethane copolymers have some amount of polyester polyurethane
incorporated into them, to improve their stability, and thereby
result in the best basecoat properties developed to date. This
alternative nonaqueous dispersion will again use the same
stabilizer as the polyurethane dispersions described above.
However, instead of using the typical polyols to react with the
diisocyanate, polyester diols are reacted with the stabilizer and
the diisocyanate. Again these diisocyanates will be those described
in the previous polyurethane system and the reaction conditions and
procedures will be the same.
These polyester diols which may be used with this reaction are
typically a reaction product of a diacid and a diol and should have
molecular weights of about 500 to about 2000 with a preferred
molecular weight range of about 600 to about 900. The reaction is
conventional and two examples of the polyester diols follow:
EXAMPLE III
To a reaction flask equipped with an agitator, nitrogen inlet tube,
thermometer and vigreaux fractionating column 513.65 gm of ethylene
glycol and 1008.9 gm of adipic acid were charged. The batch was
heated to about 145.degree. C. at which time the esterification
reaction started. The batch was heated and water was removed until
an acid number of about 5 was reached at a corresponding
temperature of about 244.degree. C. The total water removed was
about 242 gm. The resin was then cooled and resulted in a 100%
nonvolatile solid mass with an equivalent weight of 618 gm per
equivalent of hydroxyl.
EXAMPLE IV
To a reaction flask equipped with an agitator, thermocouple,
nitrogen inlet tube and fractionating column 659 gm of neopentyl
glycol, 393.5 gm of ethylene glycol and 1620 gm of adipic acid were
charged. The reaction mixture was then heated to about 150.degree.
C. at which time the esterification reaction began. The heating
continued and the water was removed from the reaction until the
batch temperature reaches about 215.degree. C. At this point the
reaction batch was cooled to less than 100.degree. C. The
fractionating column was replaced with a barret trap and 84 gm of
toluene was added to the reaction flask. The batch was then heated
to 185.degree. C. at which time the toluene and water begin to
reflux and the water was removed. The batch was held at reflux
until a total of 403 gm of water had been removed and the acid
number was less than 5. The batch was cooled to 100.degree. C. and
888 gm of N-butyl acetate was added to give a 70% nonvolatile
solution of a polyester resin with an equivalent weight of 669 gm
nonvolatile per equivalent of hydroxyl.
Typically, the proportion of reactants used to prepare the
polyester polyurethane nonaqueous dispersion will be about 20-45%
by weight of polyester diols, with about 30-40% by weight being
preferred, about 8% to about 35% by weight of the stabilizer and
about 15% by weight to about 45% of the diisocyanate. In addition
to using only the polyester diols, polyols of the type described
above may be added to complete the weight percent of the desired
polyester diol reactants.
Again it is important that the equivalent ratio of OH/.sub.NCO in
the reactants be from about 1.02 to about 1.5 with the preferred
ratio being about 1.4.
The solvents in which the resultant urethane polymer or polyester
urethane polymers are dispersed to form the nonaqueous dispersion,
should have a polarity coefficient of less than that of the
urethane or polyester urethane portion of the polymer. Typically,
these will be ketones, acetates, aromatics, etc., such as methyl
ethyl ketones, amyl acetate, and toluene. Once the particular
polymer has been synthesized, it is dispersed in the solvents to
form a nonaqueous dispersion. These particular nonaqueous
dispersions are particularly adapted for use with base coat/clear
coat finishes for the automobile industry. To prepare such coatings
the particular nonaqueous dispersion is mixed with conventional
base coat constituents such as color pigmentation, cross-linking
agents, possibly aluminum particles, UV absorbers, etc. The mixture
may then be diluted with an appropriate solvent to lower the
viscosity to an acceptable level.
EXAMPLE V
A typical base coat formulation follows: 24.2 gm of an aluminum
pigment, 0.63 gm of a UV absorber (Sandovar 3206, Sandoz Ltd.),
44.4 gm of a melamine cross-linking agent (RES-755 from Monsanto
Industrial Chemicals Company, were mixed in a slurry in a solvent
comprising 1.25 gm of N-butanol, 20 gm of N-butyl acetate and 5 gm
of high flash aromatic naptha from Ashland Chemical Corp. To this
was added a mixture of 84.7 gm of a polyester polyurethane
nonaqueous dispersion, and 3.59 gm of an acid catalyst (p-toluene
sulfuric acid) in 30 gm of N-butyl acetate and 5 gm of N-butanol.
The entire mixture was then reduced with the N-butyl acetate to a
viscosity of 21 seconds in a Fisher #2 cup for spraying onto the
substrate.
Typically, these base coats which are applied to the substrate are
sprayed on and are limited to a certain range of viscosities. The
present nonaqueous dispersions of this invention allow for lower
viscosities of the final base coat mixture with higher solids
content, thereby requiring less solvent to dilute the mixture to
the proper viscosity. In addition, these nonaqueous dispersions
allow for a base coat mixture with lower viscosities yet have
significantly higher solids contents. Typically these base coat
mixtures will contain about 40% to about 45% solids content and
still have the same viscosity as conventional base coat materials
of the prior art, typically 30% to about 35%. Additionally, the
base coats prepared using these polyurethane nonaqueous dispersions
will result in a base coat having excellent rheology control,
thereby not requiring the addition of rheology control agents which
may deteriorate the quality of the base coat/clear coat finish.
EXAMPLE VI
To a reaction vessel equipped with an agitator, condensor and water
trap, thermometer and a nitrogen inlet tube the following materials
were added: 68 gm of polyester diol of Example III, 97.2 gm of the
70% solids polyester diol of Example IV, 48 gm of 1,6 hexane diol,
24 gram of trimethylol propane, 68 gm of the 82% NV solution of
stabilizer of Example I, and 25 gm of toluene. The reaction mixture
was heated to relfux 133.degree. C. and any traces of water were
removed from the mixture. The reaction mixture was cooled to
58.degree. C. at which time 130.2 gm of toluene and 0.6 cc of
benzyl dimethlylamine were added. The reaction mixture was cooled
to 40.degree. C. and 132.7 gm of isophorone diisocyanate were added
over 15 minutes. The batch exothermed to 63.degree. C. at which
time heat was applied and the batch was heated to reflux at
121.degree. C. The batch was held at reflux until the reaction was
greater than 99% complete as determined by isocyanate analysis. The
batch was then cooled to 52.degree. C. and 17.2 gm of ethylene
glycol monobutyl ether was added. The resulting polymer dispersion
had a Gardner Holdt viscosity of Z-1 at 66% nonvolatile, at
25.degree. C.
EXAMPLE VII
To a reaction vessel equipped with an agitator, condenser and water
trap thermometer and a nitrogen inlet tube the following materials
were added: 136 gm of polyester diol of Example III, 48 gm of 1,6
hexane diol, 24 gm of trimethylol propane, 70.4 gm of the 79.5%
nonvolatile solution of stabilizer of Example II, and 25 gm of
toluene. The reaction mixture was heated to reflux (135.degree. C.)
and any traces of water were removed from the mixture. The reaction
mixture was cooled to 50.degree. C. at which time 156.8 gm of
toluene and 0.6 cc of benzyldimethylamine was added. The reaction
mixture was cooled to 40.degree. C. and 138 gm of isophorone
diisocyanate were added over twenty minutes. The batch exothermed
to 53.degree. C. at which time heat was applied and the batch was
raised to reflux at 115.degree. C. The batch was held at reflux
until the reaction was 98.8% complete as determined by isocyanate
analysis. The batch was then cooled to 70.degree. C. and 20.2 gm of
ethylene glycol monobutyl ether was added. The resulting polymer
dispersion had a Gardner Holdt viscosity of X-Y at 64.1%
nonvolatile at 25.degree. C.
It should be understood that the invention is not limited to the
particular embodiments shown and described herein, but that various
changes and modifications may be made without departing from the
spirit and scope of this novel concept as defined by the following
claims.
* * * * *